Impression coping system for osseointegrated implants

ABSTRACT

The present invention relates to a system of interchangeable impression coping for use with osseointegrated implant systems. The coping system will allow an accurate registration of the fixture head, abutement, healing abutment, or other prefabricated components to which the implant may be connected. The coping system also permits the direct substitution of each of the various impression copings within an index or impression, so as to transfer, translate or transform the relations and/or the type of component to a model adapted from an index or poured from an impression registered using the coping system.

Osseointegrated implants are fixtures commonly screwed into preparedsites in the jaw, facial, or limb bones for the retention of prostheses,e.g. dental bridges, facial prostheses, or limb prostheses. Suchprostheses are usually retained by means of screws, adhesives, ormechanical attachments to an abutment, which is itself precisely locatedon and connected to the fixture by means of an abutment screw.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a typical dental abutment of the prior art.

FIG. 2 shows prior art abutments of a type commonly used to supportdental prothesis.

FIG. 3 shows a healing abutment of the prior art.

FIG. 4 is a chart depicting the process of using the system of thepresent invention.

FIG. 5 shows an impression coping of the present invention.

FIG. 6 shows impression copings fitted on abutments of differentlengths.

FIG. 7 shows impression copings fitted on the fixture head as well as onhealing abutments of different lengths.

FIG. 8 shows an alternative embodiment of a two part impression copingseated over abutments of different lengths.

An abutment is a trans-mucosal, or trans-dermal component, usuallyfabricated from a highly bio-compatible material capable of developingsome kind of stable union with the adjacent living tissues, whichfacilitates the connection of the prosthesis to the fixture. Abutmentsmay have a precise, prefabricated external configuration which willallow the use of prefabricated “prosthetic” components which preciselyfit against the abutment for the fabrication of the prosthesisframework, or the abutment may be intended for preparation, in whichcase a framework may be constructed using conventional dental crown andbridge impression and fabrication techniques. Alternatively, aprosthesis may be fixed directly to the fixture head, usingprefabricated “prosthetic” components which precisely fit against thefixture for the fabrication of the framework.

FIG. (1) illustrates a typical dental implant, and associated componentsby way of example. The head of the fixture (1) is provided with ahexagonal external feature (2), and a screw recess (3), which togetherallow the fixture to be manipulated, and permit the connection of anabutment (4), by means of an abutment screw (5). If the abutment isdesigned to allow screw retention of a prosthesis, the head of theabutment screw may itself contain a recess (6) for a prosthesisretention screw.

FIG. (2) illustrates abutments of a type commonly used to support dentalprostheses. Both abutment types are connected to the fixture by means ofan abutment screw (21 and 22). One abutment type (23) is designed forcementation of a restoration onto a suitably shaped part (24), andanother type, (25 a and 25 b) is designed for screw retention of therestoration by means of a “prosthetic” screw which is screwed throughthe restoration into an appropriate recess in the abutment screw head(26). The abutment length in each case is 1. Apart from differences ingeneral shape, abutments of each type are available in differentlengths, as illustrated (25 a and 25 b).

The fixtures are usually placed as either a one stage surgicalprocedure, in which case the fixture, or an abutment connected to thefixture immediately protrudes through the skin or mucosa overlaying thesite, or as a two stage procedure in which case the fixture is coveredover with the overlaying tissue after installation (first stagesurgery), and left to heal undisturbed for a period, at which time asecond small surgical procedure, (second stage surgery) permits accessto the head of the fixture, and an abutment, which protrudes through thetissue, is attached.

In areas of the mouth which are not cosmetically important, or in othersituations where an abutment need not to be selected or prepared withprecision, it is often possible to select or fit an abutment at the timeof surgery, accepting that the final relationship of the abutments withthe adjacent tissue may be less then ideal. There are other situationswhere an abutment may be placed, and subsequently replaced.

However it is often more convenient to allow the tissues (i.e. thegingivae for oral implants or skin for other fixtures) to heal beforeselecting the definitive abutment to which the prosthesis will beattached, as it is only after the tissues have healed, that an abutmentof exactly the correct proportions may be predictably selected orprepared.

With this in mind, it is common practice to connect healing abutments,which are commonly formed of titanium, or a similary bio-compatiblematerial, to the fixture, until the tissue has healed, and a relativelystable soft tissue contour has established. Healing abutments may beconnected, either during one stage surgery, or at second stage surgery.

Healing abutments, which often have a solid one piece construction,usually screw into the head of the fixture and act as a solid templateagainst which the tissues can heal. FIG. (3) illustrates a healingabutment, in which, a cylindrical body (31) tapers towards the fixturehead, to which it is fixed by means of an integral abutment screw (32).A retentive feature (33) permits the healing abutment to be picked upand manipulated by a screw driver, and may permit the connection ofvarious attachments. The length of the healing abutment (1) is selectedto suit the height of the tissue collar around the fixture head. (Somehealing abutments have a two piece construction, in which case thehealing abutment per se is positioned over the head of the fixture, andmay interlock with any anti-rotational features of the fixture head, anda retaining screw may then be screwed through the abutment and into thehead of the fixture).

Once the tissues have healed an a stable tissue contour has established,and once a strong bony support for the fixture has developed, the palingabutment may be removed and the final abutment fitted.

Once the final abutment has been fitted, it is common practice for animpression to be taken so as to construct a detailed model of theprotruding abutment and the surrounding tissue. This usually involvesthe connection of precise, prefabricated impression copings to theabutments, and taking an impression which picks up the impressioncopings in such a way that the abutments may be precisely related to thesurrounding tissues, and to one another.

The impression is usually cast using an accurate material such as adental model stone to create a model upon which the prostheses can beconstructed. It is also common practice to use abutment replicas, whichmay be located within the matched impression coping so as to exactlyreplicate the important details of the abutment surface on the model.

An impression may also be registered, using impression copings which fitthe fixture head, and a model formed using fixture replicas whichemulate the relevant detail of the fixture head, facilitating theproduction of an accurate working model. A prosthesis may be constructedwhich is fitted directly onto the fixture heads, or abutments may beselected or prepared out of the patients mouth and the prosthesisconstructed on the working model with the abutments in place.

This approach may be adapted so as to permit the position of the fixtureheads to be registered upon completion of fixture installation. Thismeans that abutments may be selected, and prepared if necessary, andthen provisional or definitive restorations or prostheses fabricated,ready for insertion, either at the time of second stage surgery orfollowing healing of the gingivae or skin around the healing abutmentafter fixture installation and following stabilisation of the fixture.

It is important to note that research has demonstrated a form of tissueattachment to the commercially pure titanium surface of the tissuepenetrating abutments, and this has been shown to be somewhat fragile,as manipulating and swapping over components seems to cause loss oftissue attachment, and possibly increases remodeling of the adjacenttissues.

This invention comprises a system of interchangeable, fixture headimpression copings, abutment impression copings, and healing abutmentimpression copings, which will allow an accurate registration of thefixture head, abutment, or healing abutment, and permits the directsubstitution of each of the various impression copings within an indexor impression, so as to apparently transfer, translate, or transform therelations of, and or the component type, to a model adapted from anindex or poured from an impression registered using the coping system.This process is depicted in FIG. (4).

A specific embodiment of this invention will now be described withreference to FIGS. 5-7.

FIG. (5) illustrates an impression coping (51), height h, seated over anabutment, (52), length l, where the total height of the coping (h) plusthe abutment length (l) is equal to a standardized value. This standardvalue is equivalent to a fundamental height h_(f) which is the height ofan impression coping (53), with a recess at its base (54) which isdesigned to locate directly over a fixture head.

Thus:

h+1=h _(f)

In all cases, a standardized retentive feature (55) situated at anidentical location on each coping, permits the coping to be retained byan appropriate impression material capable of flowing into the feature.Above the retentive feature each coping is identical in size and shape.Below the retentive feature the coping is smooth sided and uniform incross-section; the width of the copings at any point is alsostandardized, and is no less than that of the largest component uponwhich it may be located.

The component fitting surface of the copings may take many forms, whichwill permit the coping to precisely locate over a fixture head,abutment, healing abutment, or any other prefabricated component whichmay be located over the fixture head. The coping may be retained byfriction or mechanical interlocking upon a retentive feature of thecomponent, or by means of a retaining screw which passes through thecoping, but maintains the standardized external dimensions and contourof the coping.

Apart from accommodating prefabricated components of different purposeand design, copings are provided of different heights, so as toaccommodate components of different lengths, such that if the length ofe.g. an abutment is increased, then the height of the coping is reducedaccordingly. FIG. (6) demonstrates how copings (IC) located on abutments(A) of different length (l) are selected such that the total height ofthe coping and abutment together is identical to that of a copinglocated on a fixture head (FH).

This principal is also applied to healing abutments. FIG. (7)demonstrates an impression coping (IC), which is fitted to a fixturehead (FH) as well as impression copings of various lengths which havebeen pushed into place on the retentive features of the occlusal aspectof healing abutments (HA) of different lengths. The external dimensionsof the coping/healing abutment combinations is analogous to that of thefixture head impression coping.

With an impression coping of the correct height seated in place over aprefabricated component located on the fixture head, or on the fixturehead itself, an impression may be taken of e.g. the jaw, which will“pick up” the impression coping as the impression material flows intothe retentive feature. The coping may then be removed from theimpression, and replaced with an alternative coping, to which anappropriate replica may be attached which will lock into place in anidentical fashion, replicating the orientation that would exist withalternative components connected to the fixture head, or replicating theorientation of the fixture head itself.

In situations where the precise orientation of the external or internalanti-rotational features of a fixture must be established, theimpression copings must also have an external shape which preventsrotation of the coping within the impression, and a component fittingsurface that engages distinct features on the component. Use of thesystem is now described by way of example, using impression taking forthe construction of a dental prosthesis as an example:

1. Fixture head impression copings may be attached to the fixture headimmediately upon installation, or at any later date, and an impressionor alternative form of index or registration taken.

Fixture head replicas may then be located within the coping, and aworking model created, upon which abutments may be prepared or attached,and restorations may be constructed. This process transfers therelations of the fixture head from patient to model.

Alternatively, the impression coping may be removed, and an abutmentlevel impression coping of particular type or length may be inserted inits place, and an appropriate abutment replica located within thecoping. A working model may then be formed, which anticipates theconnection of the planned abutments to the fixture heads, thuspermitting preliminary stages of the construction of the restoration, oreven a final restoration to be constructed, without having to handle theactual abutments in the laboratory. This process transforms andtranslates the relations of the fixture head in the jaw to a model whichaccurately demonstrates the relations that the selected abutment typewould have if located onto the fixture head.

2. Healing abutment impression copings may be located on the occlusalaspect of Healing Abutments which have been connected to the fixturehead either immediately upon installation of the fixture, or at the timeof second stage surgery, (or subsequently). An impression or alternativeform of index or registration may be taken once the soft tissues havebeen closed around the abutment at the time of surgery, or ideally aftera period of healing and tissue maturation.

The healing abutment impression coping may then be removed from theimpression, and an Abutment level or Fixture head level impressioncoping of particular type or length may be inserted in its place, anappropriate replica located within the coping. A working model may thenbe formed, which anticipates the connection of a planned abutment to thefixture head, or replicates the position of the fixture head itself.This process thus transforms and translates the relations of the healingabutment, fixture head, jaw, and adjacent soft tissue to a model whichaccurately demonstrates the relations of the fixture head, or therelations that the selected abutment type would have if located onto thefixture head.

If the tissues have been allowed to heal and mature following surgery,the final abutments may be predictably selected or prepared in theknowledge that there will be little further change in tissue contour,thus facilitating, and increasing the predictability of subsequentrestorative stages.

3. Abutment impression copings may be located on the abutments and animpression or alternative form of index or registration taken which willpick up the impression copings.

Abutment replicas may then be located within the copings, and a workingmodel formed, upon which restorations may be constructed. This processtransfers the existing relations of the abutment from patient to model.Alternatively, if there is a need to change abutments, e.g. aftershrinking of the soft tissues, the impression coping may be removed, andan abutment level impression coping of different type or length may beinserted in its place, and an appropriate abutment replica locatedwithin the coping. A working model may then be formed, which anticipatesthe replacement of the existing abutment with the planned abutment, thusminimising manipulation of components and the tissues. If necessary afixture level coping may be placed, thus permitting preparation orselection of a new abutment on a laboratory model.

For an implant system comprising of many different fixture and abutmenttypes and sizes many copings of the type described above will berequired. A further embodiment of this invention is intended to overcomethis potential drawback.

This alternative embodiment will now be described with reference to FIG.(8), in which a two part impression coping is seated over abutments ofdifferent lengths.

The main body of the coping (81) is seated over the abutment (83).Opposing vertical slots, (84 and 85) of different heights, are locatedin the walls of the coping body. The outer casing of the coping (82),fits over the body of the coping. On the inner aspect of the casing(82), spurs (86) are located such that the outer casing may be locatedover the body in two different orientations, as depicted in FIG. (8),A&B.

FIG. (8),A, shows the two part coping in place over a long abutment. Inthis case, the spurs (86) are located fully in the long slots (85), inthe body of the coping.

To convert the coping for use with a short abutment the two parts of thecoping, (81 and 82) are pulled slightly apart so that the spurs (86)disengage the slots (85). The body (81) may then be rotated within thecasing (82), such that the spurs (86) may be inserted into the shortslots (84), thus lengthening the total height of the coping, as in FIG.8,B. Different abutment heights may be catered for by varying the lengthand number of slots in the body of the coping.

To facilitate the use of the coping, markings (87) on the exterior thecoping body, which are covered, or uncovered, depending on the state ofextension of the casing, will tell the operator if the coping iscorrectly extended for use with the abutment in question.

There is also provided a fixture head coping, as depicted in FIG. (8),C.This is the fundamental coping for the system, as described elsewhere inthis text. The external profile of this coping is essentially similar tothat of the various different configurations of the two part coping andabutment or healing abutment combination; thus models may be constructedin a similar fashion to that described above.

What is claimed is:
 1. A system of interchangeable impression copingsfor use with osseointegrated implant systems, comprising: at least afirst impression coping having a component fitting surface mountable toat least a first type of component connectable to an osseointegratedimplant; and at least a second impression coping having a componentfitting surface mountable to at least a second type of said componentdifferent from said first type; wherein said first and second impressioncopings are substitutable for each other within an impression takenusing either of said first or second impression copings.
 2. The systemof claim 1, wherein said components comprise at least one of a fixturehead, abutment or healing abutment.
 3. The system of claim 1, whereinsaid impression copings are mountable to said components by means offriction, mechanical interlocking, or screw retention.
 4. The system ofclaim 1, wherein said first and second impression copings have at leastone common exterior feature, said first and second impression copingsbeing identical to each other for an extent adjacent to said commonexterior feature, for enabling said first and second impression copingsto be substitutable for each other in said impression.
 5. The system ofclaim 4, said common exterior feature comprising a retention groove. 6.The system of claim 1, wherein said first and second impression copingscomprise identical external retentive features enabling positions ofanti-rotational features of said components to be transferred to animpression.
 7. The system of claim 1, said first and second impressioncopings being mountable to a common standardized height on saidcomponents.
 8. A configurable impression coping, comprising: a body withwalls having opposing vertical slots of different lengths; and an outercasing fitting over said body and having inner spurs; wherein saidimpression coping is configurable to accommodate abutments of differentsizes by orienting said spurs to engage selected ones of said slots. 9.The configurable impression coping of claim 8, wherein said impressioncoping is retainable on said abutment by at least one of friction,mechanical interlocking, and a screw.
 10. The configurable impressioncoping of claim 8, said body comprising exterior markings for showing astate of extension of said outer casing.
 11. A method for efficientfabrication of a prosthesis model, comprising: providing a range ofimpression copings, each having a component fitting surface mountable toa different type of component connectable to an osseointegrated implant;forming an impression using a selected coping of said range ofimpression copings; replacing said selected coping in said impressionwith an alternative coping of said range of impression copings; andforming said model utilizing said impression with said alternativecoping.